The political and economic upheavals which have taken place in Eastern Europe have had an impact on radiation and nuclear safety throughout Europe. Emergency preparedness systems for unexpected nuclear events have been developed further in all European countries, and prosperous western nations have invested in improving the safety of East European nuclear power plants. The economic crisis facing countries of the former Soviet Union has also promoted illicit trade in nuclear materials; this has made it necessary for various border guards and police authorities to intensify their collaboration and to tighten border controls. On 3-4 October 1995, Finnish Centre for Radiation and Nuclear Safety (STUK) arranged a seminar on nuclear threats and emergency preparedness in Finland. In addition to STUK experts, a wide range of rescue and civil defence authorities, environmental health specialists and other persons engaged in emergency preparedness attended the seminar. The publication contains a compilation of reports presented at the seminar. The reports cover a broad spectrum of nuclear threats analyzed at STUK, the impacts of radioactive fallout on human beings and on the environment, and preparedness systems by which the harmful effects of radiation or nuclear accidents can, if necessary, be minimized. (33 figs., 5 tabs.).